The purpose of the Mouse Genetics Core is to provide routine as well as specialized support services pertaining to mice, to members of the Program Project including Projects 1, 2, 4, and 5. Almost all of the projects in this program Project make use of g enetically modified m ice. T he objective of the Core unit is to provide the following services and resources to members of the Program Project: 1. Specialized husbandry services, including cross-fostering, putting in timed matings and checking of plugs;2. Hands-on work to rederive strains for importation purposes, training and consultation for colony management, the generation, maintenance and screening of genetically modified mice;3. Genotyping of genetically modified mice;4. Equipment for microsurgery and the generation of transgenic and null mutants The Projects all make use of mice which require genotyping for each new generation. The Core will provide efficient and cost-effective genotyping services. The Core Leader, Nora Heisterkamp, has over 15 years experience with the generation and husbandry of genetically modified mice including both transgenic as well as null mutant mouse models. She will be assisted by a Res. Asst. II who will perform most of the hands-on work.